fix: ensure track name is always converted to string in TrackHeader

Convert track.name to string in all state initializations and updates
to prevent '[object Object]' rendering issues.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

components/tracks/TrackHeader.tsx

@@ -29,12 +29,12 @@ export function TrackHeader({
   onNameChange,
 }: TrackHeaderProps) {
   const [isEditingName, setIsEditingName] = React.useState(false);
-  const [nameInput, setNameInput] = React.useState(track.name);
+  const [nameInput, setNameInput] = React.useState(String(track.name || 'Untitled Track'));
   const inputRef = React.useRef<HTMLInputElement>(null);
 
   const handleNameClick = () => {
     setIsEditingName(true);
-    setNameInput(track.name);
+    setNameInput(String(track.name || 'Untitled Track'));
   };
 
   const handleNameBlur = () => {
@@ -42,7 +42,7 @@ export function TrackHeader({
     if (nameInput.trim()) {
       onNameChange(nameInput.trim());
     } else {
-      setNameInput(track.name);
+      setNameInput(String(track.name || 'Untitled Track'));
     }
   };
 
@@ -50,7 +50,7 @@ export function TrackHeader({
     if (e.key === 'Enter') {
       inputRef.current?.blur();
     } else if (e.key === 'Escape') {
-      setNameInput(track.name);
+      setNameInput(String(track.name || 'Untitled Track'));
       setIsEditingName(false);
     }
   };